[PATCH v7 0/3] devres: provide and use devm_krealloc()

[PATCH v7 0/3] devres: provide and use devm_krealloc()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Hi Greg, Andy,

this is another reworked version of devm_krealloc(). This time without the risk
of sleeping with spinlock taken but still with enough protection for the devres
list. We're using slab's ksize() to determine whether the new size is larger
than the current real size of the chunk and then either return the same pointer
or manually alloc a new, larger chunk outside of the spinlock.

===

Regular krealloc() obviously can't work with managed memory. This series
implements devm_krealloc() and adds two first users with hope that this
helper will be adopted by other drivers currently using non-managed
krealloc().

v1 -> v2:
- remove leftover call to hwmon_device_unregister() from pmbus_core.c
- add a patch extending devm_kmalloc() to handle zero size case
- use WARN_ON() instead of WARN_ONCE() in devm_krealloc() when passed
  a pointer to non-managed memory
- correctly handle the case when devm_krealloc() is passed a pointer to
  memory in .rodata (potentially returned by devm_kstrdup_const())
- correctly handle ZERO_SIZE_PTR passed as the ptr argument in devm_krealloc()

v2 -> v3:
- drop already applied patches
- collect Acks
- add an additional user in iio

v3 -> v4:
- add the kerneldoc for devm_krealloc()
- WARN() outside of spinlock
- rename local variable

v4 -> v5:
- tweak the kerneldoc

v5 -> v6:
- tweak the devres_lock handling in devm_krealloc()

v6 -> v7:
- rework devm_krealloc() to avoid calling krealloc() with spinlock taken

Bartosz Golaszewski (3):
  devres: provide devm_krealloc()
  hwmon: pmbus: use more devres helpers
  iio: adc: xilinx-xadc: use devm_krealloc()

 .../driver-api/driver-model/devres.rst        |  1 +
 drivers/base/devres.c                         | 93 +++++++++++++++++++
 drivers/hwmon/pmbus/pmbus_core.c              | 28 ++----
 drivers/iio/adc/xilinx-xadc-core.c            | 16 ++--
 include/linux/device.h                        |  2 +
 5 files changed, 113 insertions(+), 27 deletions(-)

-- 
2.26.1


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[PATCH v7 1/3] devres: provide devm_krealloc()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Implement the managed variant of krealloc(). This function works with
all memory allocated by devm_kmalloc() (or devres functions using it
implicitly like devm_kmemdup(), devm_kstrdup() etc.).

Managed realloc'ed chunks can be manually released with devm_kfree().

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 .../driver-api/driver-model/devres.rst        |  1 +
 drivers/base/devres.c                         | 93 +++++++++++++++++++
 include/linux/device.h                        |  2 +
 3 files changed, 96 insertions(+)

diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index eaaaafc21134..f318a5c0033c 100644
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -354,6 +354,7 @@ MEM
   devm_kmalloc()
   devm_kmalloc_array()
   devm_kmemdup()
+  devm_krealloc()
   devm_kstrdup()
   devm_kvasprintf()
   devm_kzalloc()
diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index ed615d3b9cf1..bfe46e83147e 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -36,6 +36,17 @@ struct devres {
 	u8 __aligned(ARCH_KMALLOC_MINALIGN) data[];
 };
 
+static struct devres *to_devres(void *data)
+{
+	return (struct devres *)((u8 *)data - ALIGN(sizeof(struct devres),
+						    ARCH_KMALLOC_MINALIGN));
+}
+
+static size_t devres_data_size(size_t total_size)
+{
+	return total_size - ALIGN(sizeof(struct devres), ARCH_KMALLOC_MINALIGN);
+}
+
 struct devres_group {
 	struct devres_node		node[2];
 	void				*id;
@@ -126,6 +137,14 @@ static void add_dr(struct device *dev, struct devres_node *node)
 	list_add_tail(&node->entry, &dev->devres_head);
 }
 
+static void replace_dr(struct device *dev,
+		       struct devres_node *old, struct devres_node *new)
+{
+	devres_log(dev, old, "REPLACE");
+	BUG_ON(!list_empty(&new->entry));
+	list_replace(&old->entry, &new->entry);
+}
+
 #ifdef CONFIG_DEBUG_DEVRES
 void * __devres_alloc_node(dr_release_t release, size_t size, gfp_t gfp, int nid,
 		      const char *name)
@@ -837,6 +856,80 @@ void *devm_kmalloc(struct device *dev, size_t size, gfp_t gfp)
 }
 EXPORT_SYMBOL_GPL(devm_kmalloc);
 
+/**
+ * devm_krealloc - Resource-managed krealloc()
+ * @dev: Device to re-allocate memory for
+ * @ptr: Pointer to the memory chunk to re-allocate
+ * @new_size: New allocation size
+ * @gfp: Allocation gfp flags
+ *
+ * Managed krealloc(). Resizes the memory chunk allocated with devm_kmalloc().
+ * Behaves similarly to regular krealloc(): if @ptr is NULL or ZERO_SIZE_PTR,
+ * it's the equivalent of devm_kmalloc(). If new_size is zero, it frees the
+ * previously allocated memory and returns ZERO_SIZE_PTR. This function doesn't
+ * change the order in which the release callback for the re-alloc'ed devres
+ * will be called (except when falling back to devm_kmalloc() or when freeing
+ * resources when new_size is zero). The contents of the memory are preserved
+ * up to the lesser of new and old sizes.
+ */
+void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
+{
+	size_t total_new_size, total_old_size;
+	struct devres *old_dr, *new_dr;
+	unsigned long flags;
+
+	if (unlikely(!new_size)) {
+		devm_kfree(dev, ptr);
+		return ZERO_SIZE_PTR;
+	}
+
+	if (unlikely(ZERO_OR_NULL_PTR(ptr)))
+		return devm_kmalloc(dev, new_size, gfp);
+
+	if (WARN_ON(is_kernel_rodata((unsigned long)ptr)))
+		/*
+		 * We cannot reliably realloc a const string returned by
+		 * devm_kstrdup_const().
+		 */
+		return NULL;
+
+	if (!check_dr_size(new_size, &total_new_size))
+		return NULL;
+
+	total_old_size = ksize(to_devres(ptr));
+
+	/*
+	 * If new size is smaller or equal to the actual number of bytes
+	 * allocated previously - just return the same pointer.
+	 */
+	if (total_new_size <= total_old_size)
+		return ptr;
+
+	new_dr = alloc_dr(devm_kmalloc_release,
+			  total_new_size, gfp, dev_to_node(dev));
+	if (!new_dr)
+		return NULL;
+
+	spin_lock_irqsave(&dev->devres_lock, flags);
+
+	old_dr = find_dr(dev, devm_kmalloc_release, devm_kmalloc_match, ptr);
+	if (!old_dr) {
+		spin_unlock_irqrestore(&dev->devres_lock, flags);
+		devres_free(new_dr);
+		WARN(1, "Memory chunk not managed or managed by a different device.");
+		return NULL;
+	}
+
+	replace_dr(dev, &old_dr->node, &new_dr->node);
+
+	spin_unlock_irqrestore(&dev->devres_lock, flags);
+
+	memcpy(new_dr->data, old_dr->data, devres_data_size(total_old_size));
+	kfree(old_dr);
+	return new_dr->data;
+}
+EXPORT_SYMBOL_GPL(devm_krealloc);
+
 /**
  * devm_kstrdup - Allocate resource managed space and
  *                copy an existing string into that.
diff --git a/include/linux/device.h b/include/linux/device.h
index ca18da4768e3..5da7d5f0a7ff 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -206,6 +206,8 @@ int devres_release_group(struct device *dev, void *id);
 
 /* managed devm_k.alloc/kfree for device drivers */
 void *devm_kmalloc(struct device *dev, size_t size, gfp_t gfp) __malloc;
+void *devm_krealloc(struct device *dev, void *ptr, size_t size,
+		    gfp_t gfp) __must_check;
 __printf(3, 0) char *devm_kvasprintf(struct device *dev, gfp_t gfp,
 				     const char *fmt, va_list ap) __malloc;
 __printf(3, 4) char *devm_kasprintf(struct device *dev, gfp_t gfp,
-- 
2.26.1


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[PATCH v7 2/3] hwmon: pmbus: use more devres helpers

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Shrink pmbus code by using devm_hwmon_device_register_with_groups()
and devm_krealloc() instead of their non-managed variants.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/pmbus/pmbus_core.c | 28 +++++++++-------------------
 1 file changed, 9 insertions(+), 19 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 44535add3a4a..91839979cf6c 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -1018,9 +1018,9 @@ static int pmbus_add_attribute(struct pmbus_data *data, struct attribute *attr)
 {
 	if (data->num_attributes >= data->max_attributes - 1) {
 		int new_max_attrs = data->max_attributes + PMBUS_ATTR_ALLOC_SIZE;
-		void *new_attrs = krealloc(data->group.attrs,
-					   new_max_attrs * sizeof(void *),
-					   GFP_KERNEL);
+		void *new_attrs = devm_krealloc(data->dev, data->group.attrs,
+						new_max_attrs * sizeof(void *),
+						GFP_KERNEL);
 		if (!new_attrs)
 			return -ENOMEM;
 		data->group.attrs = new_attrs;
@@ -2534,7 +2534,7 @@ int pmbus_do_probe(struct i2c_client *client, const struct i2c_device_id *id,
 
 	ret = pmbus_find_attributes(client, data);
 	if (ret)
-		goto out_kfree;
+		return ret;
 
 	/*
 	 * If there are no attributes, something is wrong.
@@ -2542,35 +2542,27 @@ int pmbus_do_probe(struct i2c_client *client, const struct i2c_device_id *id,
 	 */
 	if (!data->num_attributes) {
 		dev_err(dev, "No attributes found\n");
-		ret = -ENODEV;
-		goto out_kfree;
+		return -ENODEV;
 	}
 
 	data->groups[0] = &data->group;
 	memcpy(data->groups + 1, info->groups, sizeof(void *) * groups_num);
-	data->hwmon_dev = hwmon_device_register_with_groups(dev, client->name,
-							    data, data->groups);
+	data->hwmon_dev = devm_hwmon_device_register_with_groups(dev,
+					client->name, data, data->groups);
 	if (IS_ERR(data->hwmon_dev)) {
-		ret = PTR_ERR(data->hwmon_dev);
 		dev_err(dev, "Failed to register hwmon device\n");
-		goto out_kfree;
+		return PTR_ERR(data->hwmon_dev);
 	}
 
 	ret = pmbus_regulator_register(data);
 	if (ret)
-		goto out_unregister;
+		return ret;
 
 	ret = pmbus_init_debugfs(client, data);
 	if (ret)
 		dev_warn(dev, "Failed to register debugfs\n");
 
 	return 0;
-
-out_unregister:
-	hwmon_device_unregister(data->hwmon_dev);
-out_kfree:
-	kfree(data->group.attrs);
-	return ret;
 }
 EXPORT_SYMBOL_GPL(pmbus_do_probe);
 
@@ -2580,8 +2572,6 @@ int pmbus_do_remove(struct i2c_client *client)
 
 	debugfs_remove_recursive(data->debugfs);
 
-	hwmon_device_unregister(data->hwmon_dev);
-	kfree(data->group.attrs);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pmbus_do_remove);
-- 
2.26.1


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[PATCH v7 3/3] iio: adc: xilinx-xadc: use devm_krealloc()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Use the managed variant of krealloc() and shrink the code a bit.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/adc/xilinx-xadc-core.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c
index d0b7ef296afb..f93c34fe5873 100644
--- a/drivers/iio/adc/xilinx-xadc-core.c
+++ b/drivers/iio/adc/xilinx-xadc-core.c
@@ -1092,6 +1092,7 @@ MODULE_DEVICE_TABLE(of, xadc_of_match_table);
 static int xadc_parse_dt(struct iio_dev *indio_dev, struct device_node *np,
 	unsigned int *conf)
 {
+	struct device *dev = indio_dev->dev.parent;
 	struct xadc *xadc = iio_priv(indio_dev);
 	struct iio_chan_spec *channels, *chan;
 	struct device_node *chan_node, *child;
@@ -1136,7 +1137,8 @@ static int xadc_parse_dt(struct iio_dev *indio_dev, struct device_node *np,
 		*conf |= XADC_CONF0_MUX | XADC_CONF0_CHAN(ext_mux_chan);
 	}
 
-	channels = kmemdup(xadc_channels, sizeof(xadc_channels), GFP_KERNEL);
+	channels = devm_kmemdup(dev, xadc_channels,
+				sizeof(xadc_channels), GFP_KERNEL);
 	if (!channels)
 		return -ENOMEM;
 
@@ -1172,8 +1174,9 @@ static int xadc_parse_dt(struct iio_dev *indio_dev, struct device_node *np,
 	of_node_put(chan_node);
 
 	indio_dev->num_channels = num_channels;
-	indio_dev->channels = krealloc(channels, sizeof(*channels) *
-					num_channels, GFP_KERNEL);
+	indio_dev->channels = devm_krealloc(dev, channels,
+					    sizeof(*channels) * num_channels,
+					    GFP_KERNEL);
 	/* If we can't resize the channels array, just use the original */
 	if (!indio_dev->channels)
 		indio_dev->channels = channels;
@@ -1225,14 +1228,14 @@ static int xadc_probe(struct platform_device *pdev)
 
 	ret = xadc_parse_dt(indio_dev, pdev->dev.of_node, &conf0);
 	if (ret)
-		goto err_device_free;
+		return ret;
 
 	if (xadc->ops->flags & XADC_FLAGS_BUFFERED) {
 		ret = iio_triggered_buffer_setup(indio_dev,
 			&iio_pollfunc_store_time, &xadc_trigger_handler,
 			&xadc_buffer_ops);
 		if (ret)
-			goto err_device_free;
+			return ret;
 
 		xadc->convst_trigger = xadc_alloc_trigger(indio_dev, "convst");
 		if (IS_ERR(xadc->convst_trigger)) {
@@ -1350,8 +1353,6 @@ static int xadc_probe(struct platform_device *pdev)
 err_triggered_buffer_cleanup:
 	if (xadc->ops->flags & XADC_FLAGS_BUFFERED)
 		iio_triggered_buffer_cleanup(indio_dev);
-err_device_free:
-	kfree(indio_dev->channels);
 
 	return ret;
 }
@@ -1371,7 +1372,6 @@ static int xadc_remove(struct platform_device *pdev)
 	cancel_delayed_work_sync(&xadc->zynq_unmask_work);
 	clk_disable_unprepare(xadc->clk);
 	kfree(xadc->data);
-	kfree(indio_dev->channels);
 
 	return 0;
 }
-- 
2.26.1


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Re: [PATCH v7 1/3] devres: provide devm_krealloc()

[Andy Shevchenko]

On Mon, Aug 17, 2020 at 07:05:33PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> 
> Implement the managed variant of krealloc(). This function works with
> all memory allocated by devm_kmalloc() (or devres functions using it
> implicitly like devm_kmemdup(), devm_kstrdup() etc.).
> 
> Managed realloc'ed chunks can be manually released with devm_kfree().

Thanks for an update! My comments / questions below.

...

> +static struct devres *to_devres(void *data)
> +{
> +	return (struct devres *)((u8 *)data - ALIGN(sizeof(struct devres),
> +						    ARCH_KMALLOC_MINALIGN));

Do you really need both explicit castings?

> +}

...

> +	total_old_size = ksize(to_devres(ptr));

But how you can guarantee this pointer:
 - belongs to devres,
 - hasn't gone while you run a ksize()?

...

> +	new_dr = alloc_dr(devm_kmalloc_release,
> +			  total_new_size, gfp, dev_to_node(dev));

Can you move some parameters to the previous line?

> +	if (!new_dr)
> +		return NULL;

...

> +	spin_lock_irqsave(&dev->devres_lock, flags);
> +
> +	old_dr = find_dr(dev, devm_kmalloc_release, devm_kmalloc_match, ptr);
> +	if (!old_dr) {
> +		spin_unlock_irqrestore(&dev->devres_lock, flags);
> +		devres_free(new_dr);
> +		WARN(1, "Memory chunk not managed or managed by a different device.");
> +		return NULL;
> +	}
> +
> +	replace_dr(dev, &old_dr->node, &new_dr->node);
> +
> +	spin_unlock_irqrestore(&dev->devres_lock, flags);
> +
> +	memcpy(new_dr->data, old_dr->data, devres_data_size(total_old_size));

But new_dr may concurrently gone at this point, no? It means memcpy() should be
under spin lock.

-- 
With Best Regards,
Andy Shevchenko



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Re: [PATCH v7 1/3] devres: provide devm_krealloc()

[Bartosz Golaszewski]

On Mon, Aug 17, 2020 at 7:43 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Mon, Aug 17, 2020 at 07:05:33PM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> >
> > Implement the managed variant of krealloc(). This function works with
> > all memory allocated by devm_kmalloc() (or devres functions using it
> > implicitly like devm_kmemdup(), devm_kstrdup() etc.).
> >
> > Managed realloc'ed chunks can be manually released with devm_kfree().
>
> Thanks for an update! My comments / questions below.
>
> ...
>
> > +static struct devres *to_devres(void *data)
> > +{
> > +     return (struct devres *)((u8 *)data - ALIGN(sizeof(struct devres),
> > +                                                 ARCH_KMALLOC_MINALIGN));
>
> Do you really need both explicit castings?
>

Yeah, we can probably drop the (struct devres *) here.

> > +}
>
> ...
>
> > +     total_old_size = ksize(to_devres(ptr));
>
> But how you can guarantee this pointer:
>  - belongs to devres,

We can only check if a chunk is dynamically allocated with ksize() -
it will return 0 if it isn't and I'll add a check for that in the next
iteration. We check whether it's a managed chunk later after taking
the lock.

>  - hasn't gone while you run a ksize()?
>

At some point you need to draw a line. In the end: how do you
guarantee a devres buffer hasn't been freed when you're using it? In
my comment to the previous version of this patch I clarified that we
need to protect all modifications of the devres linked list - we must
not realloc a chunk that contains the links without taking the
spinlock but also we must not call alloc() funcs with GFP_KERNEL with
spinlock taken. The issue we could run into is: someone modifies the
linked list by adding/removing other managed resources, not modifying
this one.

The way this function works now guarantees it but other than that:
it's up to the users to not free memory they're actively using.

> ...
>
> > +     new_dr = alloc_dr(devm_kmalloc_release,
> > +                       total_new_size, gfp, dev_to_node(dev));
>
> Can you move some parameters to the previous line?
>

Why though? It's fine this way.

> > +     if (!new_dr)
> > +             return NULL;
>
> ...
>
> > +     spin_lock_irqsave(&dev->devres_lock, flags);
> > +
> > +     old_dr = find_dr(dev, devm_kmalloc_release, devm_kmalloc_match, ptr);
> > +     if (!old_dr) {
> > +             spin_unlock_irqrestore(&dev->devres_lock, flags);
> > +             devres_free(new_dr);
> > +             WARN(1, "Memory chunk not managed or managed by a different device.");
> > +             return NULL;
> > +     }
> > +
> > +     replace_dr(dev, &old_dr->node, &new_dr->node);
> > +
> > +     spin_unlock_irqrestore(&dev->devres_lock, flags);
> > +
> > +     memcpy(new_dr->data, old_dr->data, devres_data_size(total_old_size));
>
> But new_dr may concurrently gone at this point, no? It means memcpy() should be
> under spin lock.
>

Just as I explained above: we're protecting the linked list, not the
resource itself.

Bartosz

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Re: [PATCH v7 1/3] devres: provide devm_krealloc()

[Andy Shevchenko]

On Mon, Aug 17, 2020 at 10:02:05PM +0200, Bartosz Golaszewski wrote:
> On Mon, Aug 17, 2020 at 7:43 PM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> > On Mon, Aug 17, 2020 at 07:05:33PM +0200, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

...

> > > +static struct devres *to_devres(void *data)
> > > +{
> > > +     return (struct devres *)((u8 *)data - ALIGN(sizeof(struct devres),
> > > +                                                 ARCH_KMALLOC_MINALIGN));
> >
> > Do you really need both explicit castings?
> >
> 
> Yeah, we can probably drop the (struct devres *) here.

void * -> u8 * here is also not needed, it is considered byte access IIRC.

> > > +}

...

> >  - hasn't gone while you run a ksize()?

> At some point you need to draw a line. In the end: how do you
> guarantee a devres buffer hasn't been freed when you're using it? In
> my comment to the previous version of this patch I clarified that we
> need to protect all modifications of the devres linked list - we must
> not realloc a chunk that contains the links without taking the
> spinlock but also we must not call alloc() funcs with GFP_KERNEL with
> spinlock taken. The issue we could run into is: someone modifies the
> linked list by adding/removing other managed resources, not modifying
> this one.
> 
> The way this function works now guarantees it but other than that:
> it's up to the users to not free memory they're actively using.

Thanks for clarification. I agree.

-- 
With Best Regards,
Andy Shevchenko



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Re: [PATCH v7 1/3] devres: provide devm_krealloc()

[Bartosz Golaszewski]

On Tue, Aug 18, 2020 at 10:40 AM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Mon, Aug 17, 2020 at 10:02:05PM +0200, Bartosz Golaszewski wrote:
> > On Mon, Aug 17, 2020 at 7:43 PM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > > On Mon, Aug 17, 2020 at 07:05:33PM +0200, Bartosz Golaszewski wrote:
> > > > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>
> ...
>
> > > > +static struct devres *to_devres(void *data)
> > > > +{
> > > > +     return (struct devres *)((u8 *)data - ALIGN(sizeof(struct devres),
> > > > +                                                 ARCH_KMALLOC_MINALIGN));
> > >
> > > Do you really need both explicit castings?
> > >
> >
> > Yeah, we can probably drop the (struct devres *) here.
>
> void * -> u8 * here is also not needed, it is considered byte access IIRC.
>

Actually it turns out that while we don't need the (void *) -> (u8 *)
casting, we must cast to (struct devres *) or the following error is
produced:

drivers/base/devres.c: In function ‘to_devres’:
drivers/base/devres.c:41:21: error: returning ‘u8 *’ {aka ‘unsigned
char *’} from a function with incompatible return type ‘struct devres
*’ [-Werror=incompatible-pointer-types]
  return ((u8 *)data - ALIGN(sizeof(struct devres),
         ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        ARCH_KMALLOC_MINALIGN));
        ~~~~~~~~~~~~~~~~~~~~~~~

Bart

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Re: [PATCH v7 1/3] devres: provide devm_krealloc()

[Andy Shevchenko]

On Tue, Aug 18, 2020 at 06:27:12PM +0200, Bartosz Golaszewski wrote:
> On Tue, Aug 18, 2020 at 10:40 AM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> >
> > On Mon, Aug 17, 2020 at 10:02:05PM +0200, Bartosz Golaszewski wrote:
> > > On Mon, Aug 17, 2020 at 7:43 PM Andy Shevchenko
> > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > On Mon, Aug 17, 2020 at 07:05:33PM +0200, Bartosz Golaszewski wrote:
> > > > > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> >
> > ...
> >
> > > > > +static struct devres *to_devres(void *data)
> > > > > +{
> > > > > +     return (struct devres *)((u8 *)data - ALIGN(sizeof(struct devres),
> > > > > +                                                 ARCH_KMALLOC_MINALIGN));
> > > >
> > > > Do you really need both explicit castings?
> > > >
> > >
> > > Yeah, we can probably drop the (struct devres *) here.
> >
> > void * -> u8 * here is also not needed, it is considered byte access IIRC.
> >
> 
> Actually it turns out that while we don't need the (void *) -> (u8 *)
> casting, we must cast to (struct devres *) or the following error is
> produced:
> 
> drivers/base/devres.c: In function ‘to_devres’:
> drivers/base/devres.c:41:21: error: returning ‘u8 *’ {aka ‘unsigned
> char *’} from a function with incompatible return type ‘struct devres
> *’ [-Werror=incompatible-pointer-types]
>   return ((u8 *)data - ALIGN(sizeof(struct devres),
>          ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>         ARCH_KMALLOC_MINALIGN));
>         ~~~~~~~~~~~~~~~~~~~~~~~

Of course, you have to drop u8 * casting as well.

-- 
With Best Regards,
Andy Shevchenko



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Re: [PATCH v7 1/3] devres: provide devm_krealloc()

[Bartosz Golaszewski]

On Tue, Aug 18, 2020 at 7:19 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Tue, Aug 18, 2020 at 06:27:12PM +0200, Bartosz Golaszewski wrote:
> > On Tue, Aug 18, 2020 at 10:40 AM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > >
> > > On Mon, Aug 17, 2020 at 10:02:05PM +0200, Bartosz Golaszewski wrote:
> > > > On Mon, Aug 17, 2020 at 7:43 PM Andy Shevchenko
> > > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > > On Mon, Aug 17, 2020 at 07:05:33PM +0200, Bartosz Golaszewski wrote:
> > > > > > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> > >
> > > ...
> > >
> > > > > > +static struct devres *to_devres(void *data)
> > > > > > +{
> > > > > > +     return (struct devres *)((u8 *)data - ALIGN(sizeof(struct devres),
> > > > > > +                                                 ARCH_KMALLOC_MINALIGN));
> > > > >
> > > > > Do you really need both explicit castings?
> > > > >
> > > >
> > > > Yeah, we can probably drop the (struct devres *) here.
> > >
> > > void * -> u8 * here is also not needed, it is considered byte access IIRC.
> > >
> >
> > Actually it turns out that while we don't need the (void *) -> (u8 *)
> > casting, we must cast to (struct devres *) or the following error is
> > produced:
> >
> > drivers/base/devres.c: In function ‘to_devres’:
> > drivers/base/devres.c:41:21: error: returning ‘u8 *’ {aka ‘unsigned
> > char *’} from a function with incompatible return type ‘struct devres
> > *’ [-Werror=incompatible-pointer-types]
> >   return ((u8 *)data - ALIGN(sizeof(struct devres),
> >          ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >         ARCH_KMALLOC_MINALIGN));
> >         ~~~~~~~~~~~~~~~~~~~~~~~
>
> Of course, you have to drop u8 * casting as well.
>

Yes, of course. Duh

Bart

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Re: [PATCH v7 1/3] devres: provide devm_krealloc()

[Andy Shevchenko]

On Tue, Aug 18, 2020 at 08:13:10PM +0200, Bartosz Golaszewski wrote:
> On Tue, Aug 18, 2020 at 7:19 PM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> > On Tue, Aug 18, 2020 at 06:27:12PM +0200, Bartosz Golaszewski wrote:
> > > On Tue, Aug 18, 2020 at 10:40 AM Andy Shevchenko
> > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > On Mon, Aug 17, 2020 at 10:02:05PM +0200, Bartosz Golaszewski wrote:
> > > > > On Mon, Aug 17, 2020 at 7:43 PM Andy Shevchenko
> > > > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > > > On Mon, Aug 17, 2020 at 07:05:33PM +0200, Bartosz Golaszewski wrote:
> > > > > > > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

...

> > > > > > > +static struct devres *to_devres(void *data)
> > > > > > > +{
> > > > > > > +     return (struct devres *)((u8 *)data - ALIGN(sizeof(struct devres),
> > > > > > > +                                                 ARCH_KMALLOC_MINALIGN));
> > > > > >
> > > > > > Do you really need both explicit castings?
> > > > > >
> > > > >
> > > > > Yeah, we can probably drop the (struct devres *) here.
> > > >
> > > > void * -> u8 * here is also not needed, it is considered byte access IIRC.
> > > >
> > >
> > > Actually it turns out that while we don't need the (void *) -> (u8 *)
> > > casting, we must cast to (struct devres *) or the following error is
> > > produced:
> > >
> > > drivers/base/devres.c: In function ‘to_devres’:
> > > drivers/base/devres.c:41:21: error: returning ‘u8 *’ {aka ‘unsigned
> > > char *’} from a function with incompatible return type ‘struct devres
> > > *’ [-Werror=incompatible-pointer-types]
> > >   return ((u8 *)data - ALIGN(sizeof(struct devres),
> > >          ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >         ARCH_KMALLOC_MINALIGN));
> > >         ~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Of course, you have to drop u8 * casting as well.
> >
> 
> Yes, of course. Duh

With this addressed (and don't forget to remove also unneeded parentheses),
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Thanks!

-- 
With Best Regards,
Andy Shevchenko



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